The invention described herein relates generally to inertial confinement fusion (ICF), and more particularly to methods and apparatus for reducing the input energy requirement for driving ICF targets.
The avowed purpose of ICF is to produce relatively tiny but powerful thermonuclear explosions by imploding small DT-filled targets to ignition conditions. The very energetic thermonuclear products released from the explosions are intended to be used to produce electricity, to provide high-energy x-rays and neutrons for important scientific experiments, and to accomplish many other useful and beneficial goals. Even though ICF targets are driven by presently existing means to provide modest quantities of thermonuclear energy, the full realization of the potential of ICF will only be reached with the routine attainment of thermonuclear yields in excess of about 0.1 ton, TNT equivalent.
In operation, ICF targets are presently set and kept in motion by either one or the other of two distinctly different types of driver. As described by Nuckolls et al in Nature 239, 139 (1972), ICF targets may be driven by lasers. Alternatively, as set forth by Clauser in Phys. Rev. Lett. 35, 848 (1975), ICF targets may be driven by ion beams, where the ions may include electrons and charged atoms or groups of atoms. The gain of an ICF target is defined as the ratio of the amount of thermonuclear energy released by the target, to the amount of energy provided by the driver. The gains of all presently existing ICF target systems, be they laser or ion beam driven, are considerably less than unity. Clearly, for any ICF target system to be practically viable, its gain will have to be well in excess of unity. The gain of any ICF target system is functional of many parameters, such as uniformity of target illumination, driving pulse shape, photon energy in the case of laser drivers, and particle species and energy in the case of ion beam drivers. Additionally, with all other parameters held fixed, the gain of any ICF target system is usually increased by increasing the amount of energy provided by the driver, at least within the range of driver energies that are presently available. It is finally pointed out that the best and most efficient ICF target drivers that presently exist, even though they are incapable of providing gains of or in excess of unity, are huge and extremely complicated, extradordinarily expensive pieces of scientific apparatus--with sizes measured in hundreds of feet and costs measured in hundreds of millions of dollars.
It is, therefore, apparent that any methods or apparatus for increasing ICF target gain, while keeping the amount of available driver energy fixed, would be of extraordinary importance to making the goals of ICF more attainable.